Eyes won't reveal to you the type of punch or hit he is going to throw at you - for those you need the experience that makes you know which combinations are more likely in any given setting.

What eyes reveal is something infinitely more precious: his emotional and physical feelings and conditions.

Indeed, this is far more useful precisely in a street fight than against a pro - for a guy busy in a street fight has even less self control and self awareness so his eyes leak a lot of information.

You can tell infallibly the exact moment he is going to throw the first strike, a precious couple of seconds before he does so - provided you're used to look your opponents right in their faces when you fight, as you should.

They will tell you when he feels full of energy and about to charge you at full steam.
They will tell you when he is thinking and has not made a decision yet,
They will tell you when he has made a decision - a piece of information that is invaluable even if you don't know the exact details of what he may have decided for you know, now, that he's coming with something and right now.

But you can tell if that decision is about a withdrawal or about attacking and if about attacking his eyes will tell you if it is because he is crazy now, or because he feels confident, or because he feels desperate, or because he feels a rush of energy - all these things are precious in order for you to know whether that's the moment to counterattack or to bunk.

They will tell you when he has been shocked for an istance by one of your hits - there you go a weak spot or an opportunity window, don't stop then, keep hitting him (in the match, in the street you may kill him if you do, so you have to ponder and be used to process all these information in an instant while fighting, like a refined supercomputer in your head with an ultrafast processor quintessentially made for multitasking environments).

They will tell you when he is intimidated.
They will tell you when he is fatigued, you will be able to read the mounting shades of panic in his eyes, with all the varying degrees telling you which stage he is in, and you will know he's almost done even if he still gestures and poses and threats.
They will tell you when he is planning to flee - an unmistakable look.
They will tell you when he is planning a trick - a similar look to the former, slightly different though...

These things you will see and read and are emotional facts that provide precious intelligence - I was not saying you can tell if he hits you with a punch or a bottle (but if he has a bottle nearby, well... you know what's coming next don't you?).

There is no possibility to make a description or a portrait of these features in the eyes of human beings. You only know, if you're used to fight and spar, that they exist and are there to be read, unmistakably - because you have seen them many times and you know what they were associated with and, most of all, because you were aware of your own look and eyes when you felt all those emotions and had all those thoughts in a fight. It's like an actor that is playing with underplay and nuances, only that this is real life and no play.

For reasons I cannot explain, I know what my eyes looked like when i was in any of those conditions, I knew I had no real control on them because it would have implied a degree of micro-micromanagement that the impetus of a fight did not afford me (would be a luxury) - I knew that, and I knew it also if I had no mirror in front of me, but i felt as if i had it to the extent I could tell by his eyes that that slight nuance was the very same I leaked in that type of emotional condition so I knew now what he was feeling.

Precious, my friends - precious!!!

Call it experience, if you prefer; after all it's undoubtedly a part of that baggage.